If you’re saying goodbye to someone you might not see for long time, say farewell, preferably while waving a hankie from the Queen Mary before it sails across the Atlantic. Farewell is a fancy way to say goodbye.
A farewell is also an expression of good wishes at a parting. If you’re leaving a job after being there a long time, your co-workers might throw you a farewell party. Farewell is an expression, like "goodbye," but also a noun — if you like to leave without a lot of fuss, you don’t like long farewells. Farewell is a combination of fare and well. Fare comes from the Old English word faran, which means "to journey."